1. Field of the Invention
Embodiments of the present invention relate to a power conversion device using a bidirectional switch formed by connecting reverse-blocking insulated gate bipolar transistors in reverse parallel.
2. Description of the Background
A bidirectional switch formed by connecting reverse-blocking insulated gate bipolar transistors (RB-IGBTs) in reverse parallel, as it has low loss characteristics, is put to practical use in a power conversion device such as an inverter or a converter, as for example, shown in Japanese Patent documents JP-A-2007-288958 and JP-A-2012-029429.
The reverse-blocking insulated gate bipolar transistor is such that the size of leakage current when an on signal is given to the gate in a condition in which a reverse voltage is applied between the collector and emitter differs from the size of leakage current when an off signal is given to the gate in the same condition, and the latter is larger. An increase in the leakage current when the reverse voltage is applied causes an increase in loss. Further, the increase in loss leads to a decrease in the reliability of the reverse-blocking insulated gate bipolar transistor and a reduction in the conversion efficiency of the power conversion device.